# What is Heat exchange: Definition and 50 Discussions

A heat exchanger is a system used to transfer heat between two or more fluids. Heat exchangers are used in both cooling and heating processes. The fluids may be separated by a solid wall to prevent mixing or they may be in direct contact. They are widely used in space heating, refrigeration, air conditioning, power stations, chemical plants, petrochemical plants, petroleum refineries, natural-gas processing, and sewage treatment. The classic example of a heat exchanger is found in an internal combustion engine in which a circulating fluid known as engine coolant flows through radiator coils and air flows past the coils, which cools the coolant and heats the incoming air. Another example is the heat sink, which is a passive heat exchanger that transfers the heat generated by an electronic or a mechanical device to a fluid medium, often air or a liquid coolant.

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1. ### B Filling a bathtub (Hot water to cold water exchange)

Hey there, I honestly don’t know if this is the right place for this, but I figured I would ask. lets say you are going to take a bath, but someone just took a shower and you know your hot water heater will be running low on the goods. Just for arguments sake, let’s say you have just enough...
2. ### A Heat exchange in a thermal storage based on phase change materials

Hello, I want to model a thermal battery based on phase change materials (PCM). It is a plate heat exchanger immersed in a PCM bath. The diagram is given in the attached file. I want to determine the temperature at each moment and from everywhere in the battery. The hypotheses are the...
3. ### B Heat exchange after thermal equilibrium

In screenshot below, systems A and B are separated by an adiabatic wall initially while each of them exchanges energy with system C via a diathermic wall. Once A and B reach thermal equilibrium with C, then A,B are allowed energy exchange via a diathermic wall, and energy exchange between A and...
4. ### Need Help with Heat Exchange Calculations for Cosplay Suit Idea

Hello, I am trying to figure out if the investment into a watercooling system in a Cosplay suit would be worth it. I plan on using a water loop made by taking a "CoolShirt" https://coolshirt.com/product/white-coolwater-shirt/ and running water through it either from an ice bath in a sealed...
5. ### HVAC Attic to Pool Heat Exchange, will car radiator collect heat?

My attic gets very hot even with the exhaust fan I installed. I would like to move than heat to my swimming pool. I currently have a FAFCO solar pool heater where the pool pump pumps water up onto my roof and thru the 12' long solar panel and down back into the pool. I would like to free up roof...
6. ### Why this special case occurs in an exchange of heat

Homework Statement Hello. First of all sorry about this question, it has to do a little with heat transfer from engineering. This situation is not real, I was working in a proyect and this doubt came to me. I have a heat exchanger of parallel tubes. Water flows in a tube and oil flows in...
7. ### Calculating Heat Exchange Surface for Fluid Flow

Fluid comes in at ##T_1## and comes out at ##T_2## and I know that heat is exchanged with steam at constant ##T_{steam}##. If I want to know the Surface of the exchanger then ##US(T_{steam}-T_{fluid}) = \dot m_{fluid} cp_{fluid} (T_2-T_1)## My question is, since ##T_{fluid}## changes, which...
8. ### Finding Initial Temperature Entropy and Heat Exchange

Homework Statement A 2.45 kg aluminium pan at 155 C is plunged into 3.58 kg of water. If the entropy change of the system is 162 J/k, what is the initial temperature of the water? Homework Equations Q = mcΔT ΔS=mcln(T_2/T_1) Q_water + Q_Aluminium = 0 c water = 4184 J/kg*K c aluminium = 900...
9. ### Calculating Heat Exchange for a Water Pump

Homework Statement A pump, operating at 10 W, is used to raise the pressure of a stream of water at 2.5 mol/s from 1 bar to 2 bar. At steady state, if the water temperature should remain constant at 25oC, how much heat exchange between the pump and its surroundings is required? Note that 1 bar...
10. ### Heat exchange, emissivity and reflectance

Hi Guys I´m studying the heat exchange problem in furnaces and, to begin with, i started with Incropera´s book. One thing is actually driving me crazy On the last part of this exercise´s solution (part 3), the physical principle involved is not very clear to me. To calculate the absorptivity of...
11. ### Heat exchange in an isolated system

Homework Statement In a container of negligible mass, equal amounts (in weight) of ice at 0°C and steam at 100°C are mixed at atmospheric pressure. Assuming no heat exchange with the surroundings, what is the temperature when the system reaches equilibrium? What are the fractions of weights of...
12. ### Calculating Heat Exchange Requirements for Ethanol Condenser

Homework Statement Hi, I need someone to help me with this question. I tried to find the answer for two weeks I could not finde it. Anyone with the required experience can help! I will be so grateful. Question: A shell-and-tube heat exchanger is to act as a condenser: saturated ethyl alcohol...
13. ### Reversible heat exchange between water and ice

Homework Statement In an adiabatic container are placed , in rapid succession , a mass of ice , ##m_I= 2 kg## , at temperature ##T_I = -10 ◦C## and a mass of water , ##m_W = 1 kg## , at the temperature ##T_W = + 20 ◦C## . Determine : a) the total mass of water present in the container at...
14. ### Automotive Air speed in car radiator -- Heat Exchange calculations

Hello, this is my first post. This question is related to my final thesis. I'm calculating the heat exchange area of a radiator through heat exchange equations: Q = U*A*LMTD I have as data Q, and LMTD (this one through trivial calculations) In order to calculate U, I need the coefficients...
15. ### Compressing ideal gas, show no heat exchange

Homework Statement An ideal monatomic gas is contained in a cubic container of size ##L^3##. When ##L## is halved by reversibly applying pressure, the root mean square ##x##-component of the velocity is doubled. Show that no heat enters of leaves the system.Homework Equations ##dU = dQ -pdV##...
16. ### Heat Exchange and Efficiency in a Fridge

Homework Statement In a 30% efficient, -16°C fridge, how much electrical energy will be used up to lower the temperature of 250 mL of 75°C water? If the fridge is rated at 150 W, how long will this process take? Specific Heat Capacity of Water = 4200 J/Kg×K Specific Heat Capacity of Ice = 2000...
17. ### Enamel paints to allow heat exchange?

Hey, What type of enamel paints is suitable to paint the tube bundle in heat exchange so that it allows heat transfer (minimize heat loss in the paint)? heat conductivity is not usually mentioned in paints specifications. Thank you ..
18. ### Thermodynamics of Ideal Counterflow Heat Exchanger

I am (slowly) learning thermodynamics. I find a lot of it puzzling and makes me formulate many conjetures; I hope any of you can help me with this one about heat exchange. Let's start with this system: There is a closed hose loop filled with water; its temperature gradient goes from cold to...

Hi, Situation A: Black radiator in a room with white walls. Situation B: White radiator in a room with black walls. Which one is the most efficient situation? I know that convection is dominant if you look at a radiator, but i would like to know the answer in terms of radiation. Thank you :)...
20. ### Heat exchange for an isolated container

Short version: If I have an insulated container(box) of some specific size. The inside temperature is temperature X. Ambient temperature is Y. Also X < Y. The box starts warming up. I log the inside temperature over time with data points. How can I determine one or more of the following based...
21. ### How Does Temperature Equilibrate in Mixed Metal and Water Systems?

Homework Statement An aluminum vessel of 500 gr contains 117.5 gr water at 200C. a piece of iron of mass 200 gr and 750C is thrown inside. what's the final temperature and the water equivalent of the vessel. Homework Equations Specific heat of aluminum: 0.217 Specific heat of iron: 0.113 The...
22. ### Water to air heat exchange - imperial units doing my head in

Hey guys, newbie here and first post. I've got a (hopefully) simple question, but for some reason my brain just isn't working. I'm too used to working with metric, and even though it should be fairly simple, working with imperial units just hurts. Anyway, here's the problem: I have a specific...
23. ### Heat exchange: Water to water through jacketed pipe

Edit: I've realized that it's not called a 'jacketed pipe', but simply a double pipe heat exchanger. Apologies, English is not my first language. I have been asked to scour the webs for information about how to calculate the heat exchange in a jacketed stainless steel pipe, with hot water in...
24. ### What is the Formula for Calculating Heat Exchange in a Boiler Flue?

I have a heat exchanger for a boiler flue. The flue is connected to two big (150 HP) boilers. A boiler HP = 33,000 BTUH. The are less than 80% efficient. The heat exchanger problem is this: The Flue contains gas temps above 300 F. The CFM is problematic but apparently the actual CFM could...
25. ### Isothermal Process in a Non-Insulated Piston: Heat Exchange?

When an ideal gas expands in a piston during an isothermal process, does it necessarily absorbs heat from the surroundings in order to maintain its temperature? (Piston is not insulated). IF yes, When the same procedure is carried out in a perfectly insulated piston, then temperature drops...
26. ### Law for heat exchange and evaporation

I wonder if there is any law for heat exchange. I have learned that heat exchange between systems occurs when the temperature of respective systems differ. But in case of evaporation, the process creates a cooling effect even in an isothermal condition ( I mean by isothermal condition to be a...
27. ### Heat Transfer question regarding counterflow heat exchange.

Homework Statement A counterflow, concentric tube heat exchanger is used to cool the lubricating oil for large industrial gas turbine engine. The flow rate of cooling water through the inner tube (Di = 25 mm) is 0.2 kg/s, while the flow rate of oil through the outer annulus (Do = 45 mm) is...
28. ### Mass of object during heat exchange

Homework Statement An aluminum container with a mass of 400 g contains 200 g of water at a temperature of 18°C. After a block of iron at a temperature of 90°C is placed in the water, the final temperature of the mixture changes to 28°C. Find the mass of the iron, assuming that there is no...
29. ### Heat exchange in active system

I am trying to calculate the amount of water that would have to pass through a 200 litre tank (water inlet temp is 20degrees c) in order to cool water by 10degrees in a closed loop (in a coiled copper pipe) suspended in the tank the coil has a total length of 30 lineal m and a diametre of 20mm...
30. ### Heat Exchange: Ice added to water

Homework Statement A glass containing water is initially of temperature 20oC. The mass of the glass is 100 g and of specific heat 0.16 cal/g-co and water is of mass 200g. If 5 cubes of ice each of mass 15g will be added to the glass of water, solve for (a) The temperature of the mixture. (b)...
31. ### Change in Enthelpy with no Heat Exchange?

This is a rather general question but I'm studying for my thermodynamics final and wanted to clarify this topic. Is it possible for there to be a change in entropy in a cycle without a net exchange of heat into or out of the system? If so what may be some of the examples of this and how would...
32. ### Radiation heat exchange between two surfaces.

Homework Statement Prepairing for a test and this one came up that's confusing me. A spherical object, water cooled, with a diameter of 10 milimeters and ε = 0,9 is kept at 353 degrees Kelvin, when placed in a very large furnace where a vacuum is formed and which walls are kept at 673 degrees...
33. ### Heat exchange between body and environment

Hey guys, If I have a cube of ice at a certain T1 and I´m leaving it at ambient T, how do we measure the time required for the ice to melt? That is, how do we quantify the rate of the heat exchange between environment and ice? Thanks...
34. ### Heater - Heat Exchange Questions:

I recently acquired a few things that I'm hoping I can use to build a heater for a small area (10'H x 12'W x 12'L). Things I current have: 1. 20 gallons of used motor oil. 2. An old 5200 BTU window AC unit. The blower components work, the coils are 'supposedly' good, but the compressor is...
35. ### Heat Exchange in airconditioner

I let the aircon cleaning crew wash my window airconditioner.. and after it was washed.. it is less cool.. maybe from a micro leak they caused. Bad. Anyway. I'm researching how aircon work and went to over a dozen sites. I'll summarize it thus and ask something. The compressor turns the...
36. ### Heat Exchange Between Air & Water: 1 Cubic Meter Each

If i have let's say have 1 cubic meter of water at a temperature of 23 degree, in a closest system connected to a 1 cubic meter of air of 20 degree, how long time does it take for the heat to balance out, the surface between the two a 1 square meter.
37. ### Heat Exchange Solutions to Improve Shop Comfort

Heat Exchanger? Greetings, after two days of testing my idea of using a stainless steel elbow as a heat exchanger and blowing the hot air into the shop does not work. On the plus side the gravity feed pellet burner works very well. I did find that considerable heat is radiating from the top of...
38. ### Heat exchange involving phase change, hot iron into water ->steam,

Homework Statement I have been working on a University Physics thermodynamics problem for over a week now, day and night. I've consulted two physics PhDs, posted on Yahoo Answers (nobody took the bait) and I'm still stuck. I just wasted an hour and a half carefully posting my problem and...
39. ### Heat Exchange between Fluids (and similar questions)

First let me apologize for any spelling mistakes as I am on a mobile device. Second I do have a few questions regarding thermodynamics for a project I would like to begin. 1) is there a way to calculate a volume of water in either the amount of time and the amount of energy required to make...
40. ### Ideal Gas PV=nRT Cycle: Heat Exchange & Entropy

Homework Statement Consider an ideal gas whose volume is initially V_0=1cm^3 that is initially at P_0=1 atmosphere. It goes through a cycle a-b-c-a where b-c is at constant temperature. 1)According to the sketch, does the system absorb or release heat? 2)Calculate the heat exchange in a...
41. ### Factors affecting heat exchange

Heat transfer is something I've been interested in since studying thermodynamics last semester, although during the course we never really covered anything much to do with what affected heat transfer. I can pretty easily understand that obviously having a higher surface area to exchange across...
42. ### Solving for Ice: Coffee Cooling With Heat Exchange

Homework Statement You are given 2.5 102 g of coffee (same specific heat as water) at 70.0°C. In order to cool this to 60.0°C, how much ice (at 0.0°C) must be added? Neglect heat content of the cup and heat exchanges with the surroundings. Homework Equations Q=(m ice)(c ice)(delta T...
43. ### How Long to Heat Ammonia Gas by 12°C with Solar Power?

Homework Statement The sun heats 2.00 x 10^2 kg of ammonia gas that is kept at constant volume in a large tank. Assuming that solar radiation of 6.00 x 10^2 W caused the heating, determine the length of time it took to raise the ammonia's temperature by 12°C. Homework Equations...
44. ### Solve Heat Exchange Problem: Steel from 25°C to 60°C

Homework Statement A block of steel dimension is 230mm*230mm*40mm=2,116,000cubic millimeters 0.00785 gram/cubic millimeters is the given steel density Using 180 degree celsius oil (density given is 0.9) to heat up the steel from 25 degree celsius to 110 degree celsius in a 10mm diameter...
45. ### Ideal heat exchange for welding cooler?

Hello, I arrived here following links to "heat exchange". I've got a small (200amp) tig welder and would like to move up to a water cooled torch. I'm building my own cooler in my workshop. I'm challenging myself to fit a cooler into the smallest package possible, the only limits being my...
46. ### Solving a Copper Metal Heat Exchange Problem: Seeking Advice

Just looking through some old papers and found a problem that I don't know how to solve. Two identical 1.0-kilogram blocks of copper metal, one initially at a temp OC and the other initially at a temp of 100C are enclosed in a perfectly insulating container. The two blocks are initially...
47. ### Heat Exchange in Mixtures & Thermodynamics

i would like to know more about the heat exchange in mixtures and thermodynamics example would be like: How much heat energy is required to change? a) 2.0kg of ice at 0 C to water at 0 C? b) 500g of water at 100 C to steam at 100 C?
48. ### Adiabatic process and heat exchange

All the places I've searched I find that the change in the internal energy for the adiabtic process is dU = C_V\,dT But I don't understand why they use C_V, neither the volume nor the preassure is constant during the adiabtic process.. I know that dU = C_V\,dT = C_p\,dT - p\,dV...
49. ### Reversible heat exchange with surroundings

why is it acceptable to assume any heat exchanged with the surroundings of a system is a reversible heat exchange? The only explanation I can find is that it's because the surroundings are essentially unchanged by the heat they absorb...but I don't understand that as an explanation. I take...
50. ### Help Needed: Solving Tf in Metal & Liquid Heat Exchange

I can't solve this problem. Could anyone help me? A piece of metal with a mass of 2kg and specific heat of 200J/kg C is initially at a temperature of 120 C. The metal is placed into an insulated container that contains a liquid of mass 4kg, a specific heat of 600J/kg C, and an initial...